Switch pool is a means for network disaster tolerance in mobile communication and is composed of a plurality of mobile switches, and the mobile switches in a switch pool collectively provide communication services for the users in the corresponding areas.
FIG. 1 illustrates the structure of a switch pool network, wherein a wireless network controller 15 and a base station controller 13 serve as wireless access nodes and are connected with all of the mobile switches 12 in the switch pool, GSM (Global System for Mobile Communications) terminal 14 or a WCDMA (Wideband CDMA) terminal 16 communicates with the mobile switch 12 through the wireless access node, i.e., communicates with the mobile switch 12 through the wireless network controller 15 or the base station controller 13. when a user terminal enters an area covered by the switch pool, the wireless network controller 15 or the base station controller 13 can determine one mobile switch in the switch pool as a selected result according to the international mobile subscriber identity (IMSI) of the user terminal, and allocate the user terminal onto the mobile switch of the switch pool for service processing through an internal algorithm.
The mobile switch 12 allocates a temporary mobile subscriber identity (TMSI) for the user terminal, and the TMSI contains a network resource identity (NRI) field, which is uniquely directed to the mobile switch 12 in the switch pool. The TMSI containing NRI will be used in the services originated subsequently by the user in the switch pools, thus ensuring that all of the subsequent services are processed in the same mobile switch 12.
It can be see from FIG. 1 that the network also comprises a home location register 11. Serving as a storage node for the permanent data of the user terminal, and the home location register 11 has a signaling connection with each mobile switch 12 in the switch pool. Moreover, in the process of location update, the mobile switch 12 can download permanent data of the user terminal from the home location register 11.
When a mobile switch 12 needs maintenance, it transfers the registered user terminal to other mobile switches 12 in the switch pool and ensures load evenness, and the above process is called as load unloading.
The flow for a mobile switch in a switch pool to unload a user terminal in the prior art will be introduced below with reference to FIG. 1 and FIG. 2, which comprises the following steps in detail:
201, a maintaining and managing tool sending an unloading command to a mobile switch 12 and all of the wireless access nodes in the switch pool;
The mobile switch in this step is just the mobile switch that needs to unload the user terminal, and thus is called in short as a mobile switch to unload.
202, during a time period of T1, the mobile switch to unload receiving a location update request from the user terminal and accepting the request, sending a location update acknowledgement to the user terminal, and allocating a new TMSI to the user terminal, wherein NRI is null network resource identity (NULL-NRI), and notifying the user terminal that the current LAI (location area identity) is a Non-Broadcast LAI, wherein the above TMSI and LAI are contained in a location update acknowledgement message;
The user terminal periodically sends a location update request, and the mobile switch to unload has to wait for the user terminal to send out the request. Generally, the time of network periodical location update of a user terminal is 30 minutes to 2 hours, and in order to ensure that all user terminals under the mobile switch to unload can be transferred to other mobile switches of the switch pool, the time T1 in step 202 should be at least 2 times as the time of periodical location update of the user terminal, i.e., the duration of T1 is 1˜4 hours.
Step 203, the user terminal receiving the location update acknowledgement, since the location area identity is a Non-Broadcast LAI, the user terminal immediately originating a location update request again; after the wireless access nodes in the switch pool receiving the new location update request, if the wireless access nodes determine that NRI thereof is NULL-NRI, then the wireless access nodes allocating the location update request to other mobile switches that are not in unloading condition;
Step 204, a new mobile switch accepting the location update, performing location update processing, and allocating TMSI for the user terminal, wherein the TMSI includes NRI of the new mobile switch; the mobile switch returning a location update acknowledgement to the user terminal, and sending the new TMSI to the user terminal;
Through steps 201˜204, the user terminals of the mobile switch to be maintained are transferred to other mobile switches, the mobile switch to unload can temporarily stop working until maintenance is completed.
In the process of carrying out the present invention, it is found that the prior art at least has the following problems: after the maintaining and managing tool sends an unloading command to the mobile switch, it has to passively wait for a location update request returned from the user terminal; it takes 1˜4 hours for all of the user terminals under the mobile switch to be completely unloaded and transferred to other mobile switches, thus causing the process of the unloading process to take too long time. Especially if the mobile switch has an emergent failure, too long unloading time will delay maintenance of the system, which causes part of users to be unable to receive services for a long time, thus reducing the degree of satisfaction of the customers.